The present invention generally relates to a crankcase ventilating system for an internal combustion engine and, more particularly, to a breather device in the internal combustion engine for lessening the change in pressure within the crankcase.
The present invention is particularly applicable to a V-type, OHC automobile engine, i.e., an automobile engine of a type employing an overhead camshaft (OHC) system and having engine cylinders in two banks arranged in a V-shaped configuration.
Of the numerous problems tackled by automobile technicians and specialists, there is a problem associated with blow-by gases leaking from the combustion chamber into the crankcase through between the piston rings and the cylinder wall. One solution to this problem includes the recirculation of the blow-by gases from the crankcase into the intake manifold together with air, ventilated from the crankcase, so that they re-enter the engine cylinders for the re-combustion therein. On the other hand, it is well known that the pressure within the crankcase is susceptible to change under the influence of the pumping action of the reciprocating pistons, or the changes in amount of the blow-by gases leaking into the crankcase or for some other reasons, and therefore, where the crankcase is communicated direct with the intake manifold, the blow-by gases are apt to be introduced under varying pressure into the engine cylinder with the consequence of both the reduced engine operating performance and the increased oil consumption.
In view of the foregoing, the currently employed solution to the problem of the blow-by gases is generally accompanied by the employment of a breather chamber (pressure buffer chamber) in the fluid circuit between the crankcase and the intake manifold for lessening the change in pressure within the crankcase.
For example, the Japanese Patent Publication No. 52-39983, published Oct. 8, 1977, discloses the use of the breather chamber defined in the crankcase of the V-type internal combustion engine at each outer side of the respective banks of engine cylinders. The breather chambers disclosed therein are constituted by cavities formed during the casting of the engine cylinder block structure and subsequently closed by respective lids. It has, however, been found that, since the breather chambers are defined at the outer sides of the respective cylinder banks, the walls defining the breather chambers tend to protrude outwards increasing the size of the engine as a whole particularly where the respective volumes of the breather chambers are increased for increasing not only the capability of lessening the change in pressure within the crankcase brought about by the blow-by gases but also the capability of separating oil from the oil-laden medium coming from the crankcase. The increased size of the engine ofren imposes a limitation on the set-up and installation of some operatively associated instruments and pipings around the engine within a limited surrounding space.